Node or NodeI ?

[rc_hz]

Page 368 in Ice 3.1.0 document:

12.8.1Instantiating a Servant
  Instantiating a servant means to allocate an instance:    
      Node servant = new NodeI("Fred");
      
  This code creates a new NodeI instance and assigns its address to a reference of 
  type Node. This works because NodeI is derived from Node, so a Node reference
  can refer to an instance of type NodeI. However, if we want to invoke a
  member function of the NodeI class at this point, we must use a NodeI reference:
      NodeI servant = new NodeI("Fred");
  
  Whether you use a Node or a NodeI reference depends purely on whether you
  want to invoke a member function of the NodeI class: if not, a Node reference
  works just as well as a NodeI reference.

That is, the document emphasizes that if we want to invoke a member function of the XXXI class, we must use a XXXI reference instead of XXX interface reference. Can you explain a little more why ?

Further, in %ICEJ_HOME%\demo\book\simple_filesystem\Server.jav a:

	File file = new FileI("README", root);                                      
	String[] text;                                                              
	text = new String[] { "This file system contains a collection of poetry." };
	try {                                                                       
		file.write(text, null);
	} catch (GenericError e) {                                                  
		System.err.println(e.reason);                                       
	}

Are they inconsistent ?

Thank you !

[marc]

What is meant here are member functions of NodeI that are not defined in the Slice definition of Node.

[rc_hz]

What is meant here are member functions of NodeI that are not defined in the Slice definition of Node.

Thanks. So it is just a problem of inheritance. I think this paragraph is a little misleading.